Redox enzymes are enzymes which catalyze the transfer of electrons from an electron donor to an electron acceptor. In the case of phenol oxidizing enzymes, the electron donor is usually a phenolic compound and the electron acceptor is molecular oxygen or hydrogen peroxide, which is thereby reduced to H.sub.2 O. Phenol oxidizing enzymes are capable of using a wide variety of different phenolic compounds as electron donors, but they are very specific for molecular oxygen or hydrogen peroxide as the electron acceptor.
Examples of phenol oxidizing enzymes which use molecular oxygen as electron acceptor are laccases (EC 1.10.3.2), bilirubin oxidases (EC 1.3.3.5), mono phenol oxidizing enzymes (EC 1.14.18.1), catechol oxidases (EC 1.10.3.1). Phenol oxidizing enzymes which use hydrogen peroxide as electron acceptor are called peroxidases.
Phenol oxidizing enzymes can be utilised for a wide variety of applications, including the detergent industry, the paper and pulp industry (U.S. Pat. No. 4,690,895), the textile industry and the food industry. In the detergent industry, phenol oxidizing enzymes have been used for preventing the transfer of dyes in solution from one textile to another during detergent washing, an application commonly referred to as dye transfer inhibition.
For example, the use of peroxidases for bleaching fabrics during washing has been suggested in EP-A-424 398 (Novo Nordisk). WO-A-91/05839 (Novo Nordisk) describes the inhibition of dye transfer during the wash by means of peroxidase or an enzyme exhibiting oxidase activity on phenolic compounds. The compositions are said to bleach any dissolved textile dye so that no dye can redeposit upon the fabric.
It is also known that the activity of phenol oxidizing enzymes may be increased by the addition of certain organic compounds. The use of such activated enzyme systems for various purposes has also been described, for instance for inhibiting dye transfer in a washing process. The above mentioned WO-A-91/05839 (Novo Nordisk) describes that the addition of another oxidisable substrate may enhance the enzyme activity. Examples of such oxidisable substrates or "enhancers" are certain phenolic compounds, e.g. 2,4-dichlorophenol.
In three subsequent patent applications (WO-A-94/12619, WO-A-94/12620 and WO-A-94/12621, all Novo Nordisk) it is disclosed that the action of peroxidase in such anti dye-transfer compositions may be enhanced by the addition of a number of aromatic compounds, of which 2,2'-azo-bis-(3-ethylbenzo-thiazoline-6-sulphonate (ABTS) and Phenothiazine-10-propionate (PTP) appear to be the preferred compounds. WO-A-97/11217 (Novo Nordisk) discloses a process for bleaching stains by contacting the fabric in an aqueous medium with a phenol oxididizing enzyme and a "mediator", which is preferably of the phenotiazine-type.
However, some of these aromatic enhancer compounds may not be attractive as ingredients of detergent compositions for economical or environmental reasons. Furthermore, some of these enhancers like ABTS are, in their oxidized form, dyestuffs themselves. This has the disadvantage that the washed fabrics may be coloured by residual amounts of oxidised ABTS.
WO-A-97/06244 (Ciba) discloses various other compounds as enhancers for phenol oxidizing enzyme such as substituted naphtols, barbituric acids, and substituted coumarins.
Thus, although some of these approaches have been successful to a certain extent, there is still a need for alternative or improved enhancers for the activity of phenol oxidizing enzymes. In particular, there is a need for effective enzymatic bleach compositions, e.g. enzymatic bleaching detergent compositions. It is therefor an object of the present invention to provide such effective alternative or improved phenol oxidizing enzyme enhancers and enzymatic bleach compositions containing them.
We have now surprisingly found that these and other objects can be achieved by using certain N-containing compounds as phenol oxidizing enzyme enhancers.